Abwehr is a German word, which is commonly translated to the english "defence".
The head of Abwehr during World War II was Admiral Wilhelm Canaris. Under his lead, the Abwehr became a center of conspiracy against the Nazi regime. Helped by Canaris' protection, one of his subordinates, Hans Oster, helped to organise internal opposition to the Nazis. Although in April 1943, many of Oster's co-conspirators were arrested and the Abwehr was put under constant surveillance, Canaris was dismissed in February of 1944.
Abwehr has an eminent place within the psychoanalytical theory of Sigmund Freud too. Here it describes the sum of all those mechanisms, which allow the I to be protected against aversion/reluctance and fear (i.e. the german Angst).